About six percent of women 15 to 44 are affected by infertility issues, noted The Telegraph, and Science Daily noted that the reasons for infertility in 25 percent of women facing such issues were unexplained, leaving them with limited options beyond costly fertility treatments.

The PLOS One study detailed work by a team from the University of Ferrara in Italy that examined the uteruses of woman with "unexplained primary infertility," said The Telegraph. The researchers found the HHV-6A virus in 43 percent of the women examined.

"Viral infections have been considered as possible environmental factors in human infertility," said the study's authors. "In particular, herpes viruses have been implicated in male infertility, but no specific virus has yet been conclusively identified as associated with female infertility.

"In our report, 43 percent of endometrial epithelial cells from women with unexplained infertility were found positive for HHV-6A DNA, whereas no control women (with at least one previous successful pregnancy) harbored the virus."

While the virus replicates in the salivary glands, it is normally not detectable in blood or saliva.

"This is a surprising discovery," said Anthony Komaroff, a professor at Harvard Medical School who has studied HHV-6, said, according to The Telegraph. "If confirmed, the finding has the potential to improve the outcome for a large subset of infertile women."

The study's authors said, though, that additional studies were needed to confirm the association of HHV-6A infection as a cause for unexplained primary female infertility.